Objective To observe the effectiveness of early enteral nutrition (EEN) in managing ICU mechanically ventilated patients.Methods Totally 47 patients who had been ventilated for more than one week were randomly divided into EEN group and control group.The EEN group was supplied with enteral nutrition (EN) 12-24 hours after ICU admission,whereas the control group received EN 72 hours-5 days later.The function of intestinal mucosal barrier was evaluated by the reabsorb concentration of disaccharides lactulose/mannitol (L/M).In addition,the body mass index (BMI),body temperature,urine L/M ratio,serum albumin,pre-albumin,and ventilation days were recorded or calculated.Results On the seventh day,the L/M ratio was (0.036 ±0.004) in the EEN group,which was significantly lower than that (0.108 ±0.020) in the control group (t =2.746,P ＜0.01) ; the average body temperature was significantly lower in the EEN group than in the control group [(38.25 ± 1.20) ℃ vs (38.92 ± 1.40) ℃ ; t =2.683,P ＜ 0.05)] ; the incidences of adverse reactions such as constipation and diarrhea were significantly lower in the EEN group [16.7％ (4/23) vs 27.3％ (6/22),P＜0.05].The weaning rate within 2 weeks also favoured the EEN group [90％ (18/20) vs 80％ (16/20),P ＜ 0.05].Compared with the control group,the nutritional status of serum albumin and pre-albumin also showed a favourbale trends in the EEN group.Conclusions EEN can improve intestinal mucosal barrier and increase the weaning possibility in patients with mechanical ventilation.